Trading with the old gypsy to get a book of black magic

Can anyone help here , I've traded with this woman a number of times and lost my brooms all for some coins - how can I get rid of this quest and finally get the book she,s offering. I've already got one in my collections - why doesn't this one count ? Aahhhh very frustrating (!am I doing something wrong or just being a dummy ) x Valli from Brisbane 2550c7